Barometer mainstay J.P. Arencibia made mince meat out of Tampa Bay pitching in his first game in the majors Saturday, smashing two home runs in his debut for the Blue Jays. He finished 4-for-5 with three runs and three RBI, just a triple short of the cycle. With Arencibia's unprecedented success, let's see who else could be joining the fray at the big-league level.
UPGRADES
1. Jeremy Hellickson, P, TB -Jeff Niemann is on the DL, and Wade Davis could be on his way there too. As a result, arguably the best pitching prospect in the minors should get his chance to start for the Rays over the next month or two. In his first start in the bigs, Hellickson went seven strong, allowing two runs on just three hits on Aug. 2. The 23-year-old righty walked two and fanned six. He is clearly a must-own in AL-Only and keeper leagues, while he could even be a viable option in mixed leagues.
2. Jordan Lyles, P, HOU - Lyles was recently promoted to Triple-A, with the outside shot that he could see the majors before the 2010 season is through. The 20-year-old posted a 3.17 ERA and 115:35 K:BB ratio in 127 innings for Double-A Corpus Christi. The Astros might choose to be careful with their star prospect and let him spend the rest of 2010 in Triple-A, but with a struggling major league staff, a few good starts for the Express could catapult Lyles to the 'Stros by September.
3. Fernando Martinez, OF, NYM - The Mets seem to have finally embraced some sort of a youth movement, calling up Ruben Tejada and Martinez to join farm products Josh Thole, Chris Carter and Ike Davis, among others. With Jason Bay on the DL, Martinez has a chance to steal at-bats from Jeff Francoeur and prove that he will become the star that the Mets once thought he would be. I'm not sure if this will happen, but he should at least get a shot with the Mets fading down the stretch.
4. Mike Minor, P, ATL - Minor made his big-league debut Monday, and with Kris Medlen gone for the season, could cement himself as the Braves' No. 5 starter for the remainder of the season. He was a strikeout machine in the minors in 2009, fanning 146 batters in 120.1 innings between Double-A and Triple-A. The 22-year-old lefty also held minor league batters to an anemic .217 BAA. All in all, Minor has the stuff to storm the bigs like teammate Tommy Hanson did just a few seasons ago.
5. Chris Carter, 1B, OAK - Carter was finally called up to the majors with Daric Barton experiencing back spasms. Carter has been on a tear of late, batting .371/.500/.714 with three home runs and 13 RBI over his past 10 games. The 6-foot-5, 230, master blaster could see regular at-bats for the A's and has massive power potential for the rest of 2010 and into 2011.
6. Eric Thames, OF, TOR - Completely under the radar, Thames is having an outstanding 2010 campaign for Double-A New Hampshire. The 23-year-old outfielder is batting .287/.366/.514 with 21 home runs, 86 RBI and eight steals for the Fisher Cats. Although he has fanned 100 times in 110 games, the power surge from a season ago is a welcome sign, as is his health, which was a major concern in 2009. Another healthy, productive season in 2011 could make Thames a major player for the Jays.
Honorable Mention

1. Wil Myers, C, KC
2. Cory Luebke, P, SD
3. Matt Rizzotti, 1B, PHI
4. Yonder Alonso, 1B, CIN
5. Shelby Miller, P, STL
DOWNGRADES
1. Wilin Rosario, C, COL - From ecstasy to agony for Rosario, as a torn ACL will keep him out for the remainder of 2010, and possibly for the start of 2011 as well. It's a shame too, as the 21-year-old catcher was surging for Double-A Tulsa, batting .285/.342/552 with 19 home runs and 52 RBI for the Drillers. As a result of the knee injury, he might not make his big-league debut until 2012.
2. Jarred Cosart, P, PHI - A slight downgrade for Cosart, who has emerged as arguably the top pitching prospect for the Phillies. Although he was cleared by Dr. James Andrews earlier in July, he will not pitch again until the team's instructional league in autumn due to lingering elbow problems. Cosart had a 3.79 ERA and 77:16 K:BB ratio in 71.1 innings for Low-A Lakewood. He clearly wasn't going to make an impact in 2010 anyway, so don't downgrade him too much; just be cognizant of the elbow issues heading into 2011.
3. Ben Revere, OF, MIN - Revere suffered a fractured orbital bone after being hit by a pitch last week for Double-A New Britain. Although his vision appears to be fine, Revere continues to be hit by the injury bug, this after missing time for the second straight season due to a knee injury. Combined with his inability to hit for power, and Revere does not project as a superstar at the big-league level, but more of a Juan Pierre-type.
4. Jon Gaston, OF, HOU - Gaston appeared to come out of nowhere in 2009 with 35 home runs and 100 RBI for High-A Lancaster. He's come crashing back to earth in 2010 though, hitting .256/.324/.406 with nine home runs and 41 RBI through 105 games for Double-A Corpus Christi. With 89 Ks in 105 games, and a .167/.211/.278 line over his past 10 games, Gaston is looking more and more like a one-year wonder.
5. Neftali Soto, 3B, CIN - Although his power stroke has come around with age, Soto's plate discipline has not. The 21-year-old has a mere .297 on-base percentage in 107 games for High-A Lynchburg, while striking out 84 times. Over his last 10 games, he's batting an abysmal .150/.190/.225. He does have 16 home runs and 57 RBI this year, but the poor progress in his patience at the dish remains a concern.
6. Eric Arnett, P, MIL - Arnett was sent down to the AZL league to work on his miserable numbers with Low-A Wisconsin. The 2009 first-rounder posted a 7.31 ERA, but his 19:7 K:BB ratio in 16 innings convinced the Brewers that he was ready to go back. Well, in four appearances for the Rattlers, the 22-year-old righty has allowed 13 runs on 18 hits, while posting a 13:10 K:BB ratio. Overall for Low-A Wisconsin, Arnett is 0-9 with a 6.54 ERA and 56:30 K:BB ratio. He's allowed 13 home runs in 74.1 innings, and is probably wishing for 2010 to end at this point.